The invention relates to an antenna for radio reception, which is disposed, for reception of frequencies above the high-frequency range, in a motor vehicle window. This antenna is disposed together with an imprinted heating field, wherein this field extends into the vicinity of the upper window edge 12, with horizontally disposed heating conductors and with bus bars situated at the side edges of the heating field, for supplying the direct current for heating by way of high-frequency-insulating uncoupling networks. There is at least one antenna which is formed by means of connecting this heating field to an antenna connection contact by way of a conductor.
Antennas of this type are known, for example, from DE 3618452.A1 which has a corresponding patent U.S. Pat. No. 4,914,446 to Lindenmeier et al the disclosure of which is incorporated herein by reference, and from the examined patent published for public scrutiny DE 3719692 A1. In the case of these antennas, the heating field(s) on a window is/are also utilized for the reception of signals in the meter wave range, i.e. the frequency range above 30 MHz, in other words above the high-frequency range. In at least one embodiment, the antenna connections for forming diversity antennas are situated on the bus bars, in each instance, and on a point of the metallic frame that generally surrounds the entire window pane, in the form of the conductive car body, which point is adjacent to the connection point on the bus bar. In this connection, the possibility of capturing reception signals that differ from one another, for further processing in an antenna diversity system, at different locations of the bus bars and the frame, is utilized. In the case of a single-pane window, the antenna conductors and the heating conductors are conductors imprinted on the glass. To create the possibility of forming additional diversity antennas by means of electrical connections to the heating field, it is proposed in DE 3914424 C2 (which has a corresponding U.S. Pat. No. 5,097,270 which issued on Mar. 17, 1992 the disclosure of which is hereby incorporated herein by reference in its entirety) to form antenna connectors that are in part guided crosswise to the heating conductors, within the heating field, with which the antenna conductors are connected at low ohms at the intersection points. For high-frequency-type uncoupling of the bus bars from the on-board network, by way of which the direct current for heating is supplied, suitable uncoupling networks are therefore used, as they can be seen, for example, in DE 3618452, FIG. 7, blocks 6a, b, c, d, and in DE 3719692 A1, FIG. 1, blocks 6a, b, c, d. These uncoupling networks must be structured in high-ohm manner for the frequency range. This is possible with acceptable costs above the high-frequency range. At lower frequencies, the high impedance of such uncoupling networks can only be achieved at high cost and a relatively great space requirement for these networks, because of the high heating currents.